Dr. Seuss long ago passed from the scene but old manuscripts by the beloved children's author keep turning up.

Random House Children's Books said Wednesday it will publish a recently discovered manuscript with Dr. Seuss sketches, called What Pet Should I Get?, on July 28.

The publisher plans at least two more books based on materials found in 2013 by his widow, Audrey Geisel, and his secretary in the author's home in the ritzy seaside neighborhood of La Jolla in San Diego.

The author, whose real name was Theodor "Ted" Seuss Geisel, died in 1991 at the age of 87.

According to Random House, when Audrey Geisel was remodeling her home after his death, she found a box filled with pages of text and sketches and set it aside with some of her husband's other materials.

It was rediscovered 22 years later, in the fall of 2013, by Audrey Geisel and Claudia Prescott — Ted Geisel's longtime secretary and friend — when they were cleaning out his office space.

They found the full text and illustrations for What Pet Should I Get?, among other work.

"While undeniably special, it is not surprising to me that we found this because Ted always worked on multiple projects and started new things all the time — he was constantly writing and drawing and coming up with ideas for new stories," said Audrey Geisel, a vigilant keeper of her husband's legacy, in a statement.

"It is especially heartwarming for me as this year also marks twenty-five years since the publication of the last book of Ted's career, Oh, the Places You'll Go!

Susan Brandt, president of licensing and marketing of Dr. Seuss Enterprises, said she was surprised by what she found in La Jolla.

Theodor 'Ted' Seuss Geisel before his death in 1991.(Photo: Dr. Seuss Enterprises)

"Pages and pages of manuscripts and sketches were laid out on the big glass dining room table," she said in a a Random House news release. "It was truly a magical moment, and we immediately knew this was more than just a box of sketches."

Random House associate publishing director Cathy Goldsmith says What Pet Should I Get? was likely written between 1958 and 1962.

The book features the same brother and sister seen in Dr. Seuss' 1960 classic One Fish Two Fish Red Fish Blue Fish.

Why all the fuss? Because Dr. Seuss is beloved around the world, and he's big business, a perennial best seller.

Currently three of his books are in the top 50 on USA TODAY's Best-Selling Books list, boosted by the fact that March 2 is the National Education Association's Read Across America Day and a celebration of Seuss' birthday. Green Eggs and Ham is No. 16; One Fish Two Fish Red Fish Blue Fish is No. 19; and The Cat in the Hat is No. 35.

Only last year, Random House announced it would publish a book of four rediscovered illustrated stories by Dr. Seuss.

Horton and the Kwuggerbug and Other Lost Stories, published in September, contains tales originally published in Redbook magazine between 1950 and 1955, then largely forgotten.

The main story stars Seuss' faithful elephant who confronts a crafty and manipulative insect.

"Horton and the Kwuggerbug and More Lost Stories," book cover by Dr. Seuss.(Photo: Dr. Seuss Enterprises)

Charles Cohen, a scholar and collector of all-things Seussian, tracked down copies of the magazines that published Seuss.

"For the most part, those magazines were tossed out when the next month's issue arrived and the stories were largely forgotten," Cohen wrote in an introduction to the new collection.

He called the four stories "fresh encounters with old friends and familiar places."

The newly discovered Seuss materials will be kept at the University of California-San Diego, also in La Jolla, where the Dr. Seuss Collection is housed in the university's architecturally renowned central library, renamed the Geisel Library in 1995.

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He's back to enchant children again. This is the cover of the newly rediscovered book, 'What Pet Should I Get?', by the beloved Dr. Seuss, Theodor 'Ted' Geisel, who died in 1991. The manuscript and illustrations were re-discovered in 2013 by his widow, Audrey Geisel, and his longtime secretary while they were cleaning out his office in his home in the seaside La Jolla neighborhood of San Diego. It will be published by Random House in July 2015.
Dr. Seuss Enterprises

Audrey Geisel, widow of Theodor Geisel, Dr. Seuss, poses at their home in the La Jolla area of San Diego, Feb. 4, 2004. The 82-year-old heiress of Seuss world has parlayed her husband's characters into a multi-million dollar industry. More than two decades after his death, she's still finding old manuscripts to publish.
LENNY IGNELZI/ AP

Does it look like a spaceship? Students always thought so. UC San Diego's architecturally renown central library, renamed the Geisel Library in 1995, is the repository of the works of Theodor Geisel, Dr. Seuss, who lived for decades nearby in the La Jolla neighborhood of San Diego.
UCSD Libraries Commission